Belt-driven pi-pitch cycloidal propeller

ABSTRACT

A cycloidal propelling device for use on submersibles which operates in a flooded sea water environment and thereby eliminates the need for a protective sealing housing containing oil. While the propeller blades of the device are being driven in an orbital path, if a change in blade pitch is desired, a control shaft is rotated. Rotation of the blade pitch control shaft rotates a central pinion gear which drives a timing belt. Movement of the timing belt simultaneously and in synchronization rotates propeller blade gears and changes the pitch of the propeller blades which are mounted thereon with water-lubricated plastic bearings. Plug-in, pullout type plastic breakway propeller blades are used for easy repair and replacement.

United States Patent Slates 1 Feb. 1, 1972 Elmer F. Slates, Ridgecrast,Calif.

(73] Assignee: The United States of America as represented by theSecretary of the Navy [22] Filed. July 23,1970

[21] AppI.No.: 57,739

[72] Inventor:

[52] U.S.Cl ..4l6/ll1,416/2,4l6/l74,

416/241 [51] lnt.Cl B631! 1/10 [58] Field ofSearch..416/2,110,111,99,174, 224.

[56] References Cited UNITED STATES PATENTS 3,515.449 6/1970 Harbage..4l6/l74 UX 3,302,988 2/1967 Senter..... 3,233,678 2/1966 Wilk..416/241 FOREIGN PATENTS OR APPLlCATlONS 915,892 8/1946 France..416/111 Primary Examiner-Everette A. Powell, Jr. Attorney-R. S.Sciascia and Thomas 0. Watson. Jr.

{57] ABSTRACT A cycloidal propelling device for use on submersibleswhich operates in a flooded sea water environment and thereby eliminatesthe need for a protective sealing housing containing oil. While thepropeller blades of the device are being driven in an orbital path, if achange in blade pitch is desired. a control shaft is rotated. Rotationof the blade pitch control shaft rotates a central pinion gear whichdrives a timing belt. Movement of the timing belt simultaneously and insynchronization rotates propeller blade gears and changes the pitch ofthe propeller blades which are mounted thereon with wateriubricatedplastic bearings. Plug-in, pullout type plastic breakway propellerblades are used for easy repair and replacement.

6 Claims, 1 Drawing Figure PATENTED FEB 1 I972 INVENTOR.

ELMER E SLATEZS VA... 0. ma}...

ATTORNEY BELT-DRIVEN Pl-PITCH CYCLOIDAL PROPELLER STATEMENT OFGOVERNMENT INTEREST The invention described herein may be manufacturedand used by or for the Government of the United States of America forgovernmental purposes without the payment of any royalties thereon ortherefor.

BACKGROUND OF THE INVENTION The present invention relates generally toimprovements in propelling apparatus, and more particularly it pertainsto new and improved cycloidal propellers and driving means therefor.

The cycloidal propeller derives its name from the combined orbitalmotion of the propeller blades and the straight line motion of thevessel. The blades project from a rotating disc into the flow and orbitabout an axis normal to the hull surface. The angle of attack of theblades is varied in a programmed manner to produce a resultant force inany direction normal to the axis of rotation.

The pitch ratio is defined as the ratio of the propeller advance perrevolution (at zero slip) to the blade orbit radius, i.e., P=A/R, In thepresent invention, A=R by virtue of a simple belt and sun gear systemand in this manner a fixed pi-pitch propeller with the steering center(P) located at R is obtained. (To obtain cycloidal blade motion,kinematics requires that the perpendicular to the profile cord of eachblade pass through the same point, called the steering center).

Pi-pitch cycloidal propellers were used in the present inventionbecause: (I of their high theoretical efficiency, and good efficiencyover a broad speed range, (2) a cycloidal propeller can provide a 360directional control through simple blade angle changes and does notrequire reversing gears or motors (two cycloidal propellers can controla vehicle in azimuth, updown, sideways and fore and aft directions,while it would take a minimum of three reversing-less efficient-motorsand screw propellers to accomplish this), (3) cycloidal propellers havestabilizing characteristics, (4) the cycloidal propeller blades areessentially noiseless as compared to screw propellers, (5) they arereadily water flooded, lubricated and pressure compensated for unlimiteddepth applications, and (6) the friction losses of a well-designedpi'pitch cycloidal propeller are quite small as they are mechanicallymore efficient.

In the field of cycloidal propellers, it has been the general practiceto operate prior art propellers with an environmental protectedplanetary gear system and a speed-reducing gear box. To accomplish thisa pressure-compensated sealed housing unit containing oil has been used.Such devices have been unsatisfactory in that the requirement of apressure-compen' sated sealed housing to prevent destruction by the seawater environment is costly. Moreover, expensive gears with hightolerances to provide accurate meshing of the gears has been necessary.Also, the use of such intermeshing gears at times produces much noisewhen quiet operation is critical, as in some military uses. In addition,the propeller blades often become damaged and it has been difficult torepair or replace such blades.

OBJECTS OF THE INVENTION Accordingly, it is the object of the presentinvention to provide a more efficient, reliable, and less costlyoperation.

Another object is to provide a device which eliminates many moving partsand gears, is simple in construction, and is easy to manufacture.

A further object of the invention is the provision ofa timing belt whichallows the device to operate in a flooded sea water and sandyenvironment and thereby eliminates the need for a protective sealedhousing with oil heretofore required.

Still another object is to provide a srnooth-running and noiseless(noncavitating) operation due to the use of a timing belt andwater-lubricated plastic hearing at every moving part.

A still further object of the invention is to provide plastic breakawaypropeller blades which are easily repaired or replaced and are oftheplug-in, pullout type.

Other objects, advantages and novel features of the invention willbecome apparent from the following detailed description of the inventionwhen considered in conjunction with the accompanying drawings.

SUMMARY OF THE INVENTION To accomplish the above objects the pi-pitchcycloidal propeller of the present invention comprises a pluralityoftiming gears held in synchronization by means of a timing belt whichcontrols the angle of attack of the propeller blades (in this instancethree blades). The typical gearbox is eliminated and a belt-driventiming gear speed reducer is employed. The unit operates in a floodedsea water environment and thereby eliminates the sealed housingheretofore required. The water lubricates plastic bearings which areused at every moving part. The plastic bearings are critical to thesmooth and noiseless operation of the device.

The driving means for the cycloidal propeller includes a sun gear orcentral'pinion gear, which is the thrust directional controller, twoidler gears and three propeller blade gears all held in synchronizationby the timing belt. The pinion gear is one half of the diameter of thepropeller blade gears; thus for every revolution of the pinion gear (orof the main propeller disc) the symmetrical propeller blades will rotateEach blade of a pi-pitch propeller operates at a constant rotationalvelocity of one-half the propeller r.p.m. (i.e., the sun gear). A uniquetiming belt-pulley arrangement was chosen to eliminate gears and theirassociated problems.

BRIEF DESCRIPTION OF THE DRAWING The drawing illustrates an explodedperspective view of a preferred embodiment ofthe present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENT The drawing, which illustrates apreferred embodiment of the invention, shows a belt-driven cycloidalpropeller [0 including a plurality of timing gears held insynchronization by means ofa timing belt 12 which controls the angle ofattack of propeller blades [4, I6 and 18. The timing belt 12 and thegearing system are located within a one-piece cylindrical housing 20which includes a cylindrical propeller gear housing 22 and a fixedlyattached driving pulley 24,

The gearing system includes three propeller blade gears 26, 28 and 30which are symmetrically mounted within the periphery of propeller gearhousing 22. Two idler gears 32 and 34 are also mounted within housing 22to provide tension on timing belt 12.

To control the pitch movement of the timing belt 12 and propeller bladegears 26, 28 and 30, a pinion gear 36 is located in the center ofpropeller gear housing 22. The pinion gear 36 is pinned to a blade pitchcontrol shaft 38, so that rotation of shaft 38 rotates pinion gear 36and timing belt 12 to change the pitch of propeller blades 14, 16 and18.

Two propeller discs 40 and 41 are mounted on shaft 38 on both sides ofgear housing 22 and support the gearing system. The discs 40 and 41 maybe of the same diameter as gear housing 22 with holes 42 formed thereinto allow the inflow of sea water. Or, discs 40 and 41 may be of asmaller diameter than housing 22 and thereby allow sea water flooding ofgear housing 22.

Propeller disc 40 mounts the propeller blades I4, 16 and IS onwater-lubricated plastic bearings 44, 46 and 48 located in propellerdisc 40. The propeller blades [4, l6 and 18 have studs 50, 52 and 54,respectively, formed thereon for projection through their respectivebearings 44, 46 and 48 and into their respective propeller blade gears26, 28 and 30, which are in axial alignment with the bearings. Bladestuds 50, 52 and 54 are keyed to their respective propeller blade gears26, 28 and 30 in order to control the pitch of propeller blades [4, l6and I8. Slots 56 are formed in propeller discs .40 and 41 to adjusttiming belt l2.

Propeller blades l4, l6 and 18 are of the plastic breakaway type whichare easily repaired with suitable epoxy or they are easily replaced.Also, blade studs 50. 52 and 54 are of the plug-in. pullout type andprovide a detachable means of connection to propeller blade gears 26, 28and 30.

The driving assembly consists of a motor 58 which drives a belt 60. Aplastic all support bearing 62 provides a boss which is connected to theboat.

The propeller and motor housing are of sand castings of 356T6 aluminumprotected by hard anodize. The 30-inch propeller discs 40 and 41 arealso hard anodized aluminum. Water-resistant plastic is molded over thealuminum blade cores to combine the good virtues of metal and plastic.Moreover water-resistant plastic was used whenever possible to eliminatethe corrosion problem. The propeller blades [4. l6 and 18 were designedwith a modified elliptical plan form and an elliptical cord with anaspect ratio of to I.

In operation the motor 58 drives a belt 60 to rotate the onepiecehousing 20, the gearing system mounted therein, the propeller discs 40and 4t and propeller blades l4, l6 and [8. While the propeller bladegears 26, 28 and 30 are orbiting in this manner, if a change in pitch isdesired, control shaft 38 is rotated (manually or by a servomotor). Thiswill rotate central pinion gear 36 and move the timing belt 12 tosynchronize the rotation of propeller blade gears 26, 28 and 30. Sincethe propeller blades l4, l6 and 18 are keyed to gears 26, 28 and 30,they will rotate together to change the pitch of propeller blades l4, l6and [8. In this manner, the propeller blade gears are rotated to changethe pitch of the blades while they are orbiting with the housing 20.

From the above description it is apparent that the cycloidal propellerof the present invention accomplishes the objective of operation in aflooded sea water and sandy environment and thereby eliminates the needfor protective sealed housing and a plurality of meshing gears. Also theobjective of a smooth-running and noiseless operation is accomplishedthrough the use of a timing belt and water-lubricated plastic bearingsat every moving part.

Obviously many modifications and variations of the present invention arepossible in the light of the above teachings.

What is claimed is:

l. A cycloidal propeller and driving means therefor, comprising:

a rotatable propeller gear housing whose interior is open to a sea waterenvironment;

a plurality of timing gears mounted in said housing to rotate therewith;

a timing belt engaging said gears to hold said timing gears insynchronization;

a plurality of breakaway propeller blades detachably connected to saidtiming gears and rotatable therewith; water-lubricated plastic bearingsto mount said blades; means for rotating said gear housing; and

means for controlling the pitch of said propeller blades.

2. A cycloidal propeller and driving means therefor as recited in claimI, wherein said plurality of timing gears comprises a central piniongear and a plurality of orbiting propeller blade gears, all of which aremounted on waterlubricated plastic bearings.

3. A cycloidal propeller and driving means therefor as recited in claim2. wherein said propeller blades have keyed studs mounted thereon forplug-in, pullout type of connection to said gears.

4. A cycloidal propeller and driving means therefor as recited in claim3, wherein said pitch control means includes a shaft to rotate saidcentral pinion gear which causes said orbiting propeller blade gears torotate about their own axes and change the pitch of said rotatingpropeller blades.

5. A cycloidal propeller and driving means therefor as recited in claim2, wherein said plurality of timing gears comprises two idler gearswherein one of said idler gears is adjustably mounted to said housing.

6. A cycloidal propeller and driving means therefor as recited in claim3, wherein said propeller blades are exterior of said rotatablepropeller gear housing.

tart-it

1. A cycloidal propeller and driving means therefor, comprising: arotatable propeller gear housing whose interior is open to a sea waterenvironment; a plurality of timing gears mOunted in said housing torotate therewith; a timing belt engaging said gears to hold said timinggears in synchronization; a plurality of breakaway propeller bladesdetachably connected to said timing gears and rotatable therewith;water-lubricated plastic bearings to mount said blades; means forrotating said gear housing; and means for controlling the pitch of saidpropeller blades.
 2. A cycloidal propeller and driving means therefor asrecited in claim 1, wherein said plurality of timing gears comprises acentral pinion gear and a plurality of orbiting propeller blade gears,all of which are mounted on water-lubricated plastic bearings.
 3. Acycloidal propeller and driving means therefor as recited in claim 2,wherein said propeller blades have keyed studs mounted thereon forplug-in, pullout type of connection to said gears.
 4. A cycloidalpropeller and driving means therefor as recited in claim 3, wherein saidpitch control means includes a shaft to rotate said central pinion gearwhich causes said orbiting propeller blade gears to rotate about theirown axes and change the pitch of said rotating propeller blades.
 5. Acycloidal propeller and driving means therefor as recited in claim 2,wherein said plurality of timing gears comprises two idler gears whereinone of said idler gears is adjustably mounted to said housing.
 6. Acycloidal propeller and driving means therefor as recited in claim 3,wherein said propeller blades are exterior of said rotatable propellergear housing.